The present invention is directed generally to optical transmission systems. More particularly, the invention relates to wavelength allocation in multidimensional wavelength division multiplexed (“WDM”) optical transmission systems.
Digital technology has provided electronic access to vast amounts of information. The increased access has driven demand for faster and higher capacity electronic information processing equipment (computers) and transmission networks and systems to link the processing equipment.
In response to this demand, communications service providers have turned to optical communication systems, which have the capability to provide substantially larger information transmission capacities than traditional electrical communication systems. Information can be transported through optical systems in audio, video, data, or other signal formats analogous to electrical systems. Likewise, optical systems can be used in telephone, cable television, LAN, WAN, and MAN systems, as well as other communication systems.
Early optical transmission systems, known as space division multiplex (SDM) systems, transmitted one information signal using a single wavelength in separate waveguides, i.e. fiber optic strand. The transmission capacity of optical systems was increased by time division multiplexing (TDM) multiple low bit rate, information signals into a higher bit rate signal that can be transported on a single optical wavelength. The low bit rate information carried by the TDM optical signal can then be separated from the higher bit rate signal following transmission through the optical system.
The continued growth in traditional communications systems and the emergence of the Internet as a means for accessing data has further accelerated the demand for higher capacity communications networks. Telecommunications service providers, in particular, have looked to wavelength division multiplexing (WDM) to further increase the capacity of their existing systems.
In WDM transmission systems, pluralities of distinct TDM or SDM information signals are carried using electromagnetic waves having different wavelengths in the optical spectrum, i.e., far-UV to far-infrared. The pluralities of information carrying wavelengths are combined into a multiple wavelength WDM optical signal that is transmitted in a single waveguide. In this manner, WDM systems can increase the transmission capacity of existing SDM/TDM systems by a factor equal to the number of wavelengths used in the WDM system.
Optical WDM systems are presently deployed as in point-to-point WDM serial optical links (“PTP-WDM”) interconnected by electrical regenerators and switches. At each regenerator in the PTP-WDM systems, the information being transmitted can be merely regenerated on the same wavelength and retransmitted through the next link or electrically switched to one of a plurality of links, different fiber, and/or a different wavelength. Various electrical switch devices can be used to switch the information between the different links at each regeneration site.
As would be expected, the cost of performing optical-electrical-optical conversions in PTP-WDM systems becomes extremely expensive merely to route traffic through a network. The cost of electrical regeneration/switching in WDM systems will only continue to grow with WDM systems having increasing number of optical signal channels, or wavelengths. As such, there is a desire to eliminate unnecessary, and costly, electrical switching of information being transported in optical systems.
Numerous optical cross-connect switches have been proposed as alternatives to electrical switching. For example, U.S. Pat. Nos. 4,821,255, 5,446,809, 5,627,925 disclose various optical switch devices. A difficulty with optical cross-connect switches is that the switches become overly complex as the number of optical channels and input/output ports on the device is increased.
As the need for high capacity WDM systems continues to grow, it will become increasingly beneficial to provide all-optical networks that eliminate the need for electrical conversion to perform signal routing and grooming in the networks. The development of multi-dimensional all-optical networks will provide the cost and performance characteristics required to further development of high capacity, more versatile, longer distance communication systems.